U.S. patent application number 13/446555 was filed with the patent office on 2013-10-17 for apparatus and methods for calibrating analog circuitry in an integrated circuit.
The applicant listed for this patent is Neville CARVALHO, Tim Tri HOANG, Sergey SHUMARAYEV. Invention is credited to Neville CARVALHO, Tim Tri HOANG, Sergey SHUMARAYEV.
Application Number | 20130275071 13/446555 |
Document ID | / |
Family ID | 47997258 |
Filed Date | 2013-10-17 |
United States Patent
Application |
20130275071 |
Kind Code |
A1 |
CARVALHO; Neville ; et
al. |
October 17, 2013 |
APPARATUS AND METHODS FOR CALIBRATING ANALOG CIRCUITRY IN AN
INTEGRATED CIRCUIT
Abstract
The present disclosure provides apparatus and methods for the
calibration of analog circuitry on an integrated circuit. One
embodiment relates to a method of calibrating analog circuitry
within an integrated circuit. A microcontroller that is embedded in
the integrated circuit is booted up. A reset control signal is sent
to reset an analog circuit in the integrated circuit, and a
response signal for the analog circuit is monitored by the
microcontroller. Based on the response signal, a calibration
parameter for the analog circuit is determined, and the analog
circuit is configured using the calibration parameter. Other
embodiments, aspects and features are also disclosed.
Inventors: |
CARVALHO; Neville;
(Saratoga, CA) ; HOANG; Tim Tri; (San Jose,
CA) ; SHUMARAYEV; Sergey; (Los Altos Hills,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CARVALHO; Neville
HOANG; Tim Tri
SHUMARAYEV; Sergey |
Saratoga
San Jose
Los Altos Hills |
CA
CA
CA |
US
US
US |
|
|
Family ID: |
47997258 |
Appl. No.: |
13/446555 |
Filed: |
April 13, 2012 |
Current U.S.
Class: |
702/107 |
Current CPC
Class: |
G01R 35/005 20130101;
H04B 17/11 20150115; G12B 13/00 20130101; H04B 17/21 20150115; G01R
35/00 20130101 |
Class at
Publication: |
702/107 |
International
Class: |
G01R 35/00 20060101
G01R035/00 |
Claims
1. A method of calibrating analog circuitry within an integrated
circuit, the method comprising: booting up a microcontroller that
is embedded in the integrated circuit; sending a reset control
signal to reset an analog circuit in the integrated circuit;
monitoring a response signal of the analog circuit by the
microcontroller; determining a calibration parameter for the analog
circuit based on the response signal; and configuring the analog
circuit using the calibration parameter.
2. The method of claim 1, wherein booting up the microcontroller
comprises loading boot code from a programmer object file to memory
of the microcontroller and resetting the microcontroller.
3. The method of claim 1, wherein a common bus couples the
microcontroller to a plurality of analog circuits to be
calibrated.
4. The method of claim 1, wherein the response signal for the
analog circuit is generated in response to variation of a control
parameter of the analog circuit.
5. The method of claim 1, wherein the response signal of the analog
circuit is communicated to the microcontroller using a shift
register.
6. The method claim 1 further comprising: communicating a signal
from the microcontroller to a core of the integrated circuit, the
signal indicating that calibration of the analog circuit is
complete.
7. The method of claim 1 further comprising: repeating the sending,
monitoring, determining, and configuring for a plurality of analog
circuits.
8. The method of claim 7, wherein the plurality of analog circuits
are of a circuit type from a group of circuit types consisting of
comparators, phase detectors, sense amplifiers, and voltage
regulators.
9. The method claim 7 further comprising: communicating a signal
from the microcontroller to a core of the integrated circuit, the
signal indicating that calibration of the plurality of analog
circuits is complete.
10. The method of claim 1, wherein the reset control signal is sent
to a plurality of analog circuits of a same type in the integrated
circuit such that calibration-related processes for the plurality
of analog circuits proceed in parallel, further comprising waiting
to receive response signals for the plurality of analog circuits,
wherein a response signal for an individual analog circuit is
received after a calibration-related process for the individual
analog circuit is done.
11. The method of claim 10, wherein, after the response signal for
the individual analog circuit is received, the method further
comprises: configuring the individual analog circuit; determining
if all analog circuits of the plurality of analog circuits have
been configured; and waiting to receive further response signals if
not all of the plurality of analog circuits have been
configured.
12. An integrated circuit comprising: a core of the integrated
circuit; a microcontroller that is embedded in the integrated
circuit, the microcontroller including a processing unit and
memory; a controller block arranged to receive boot code for the
microcontroller from a programmer object file and store the boot
code in the memory for the microcontroller; a plurality of
sub-modules which include analog circuitry; and a common bus
arranged to communicatively interconnect the microcontroller with
the plurality of sub-modules for calibration of the analog
circuitry.
13. The integrated circuit of claim 12 further comprising:
interface circuitry arranged between the common bus and the
plurality of sub-modules, wherein the interface circuitry includes
a shift register to communicate test data from the plurality of
sub-modules to the common bus, a shift register to communicate
calibration control signals from the common bus to the plurality of
sub-modules, and a reset control circuit to controllably reset an
analog circuit within the sub-modules.
14. The integrated circuit of claim 13, wherein the interface
circuitry further includes a memory-mapped port for addressing the
plurality of sub-modules by way of the common bus.
15. The integrated circuit of claim 12 further comprising: a debug
module arranged for debugging the processing unit using a boundary
scan test system.
16. The integrated circuit of claim 12, wherein the core comprises
a programmable logic array, and the analog circuitry within the
plurality of sub-modules include circuits from a group of circuits
consisting of comparators, phase detectors, sense amplifiers, and
voltage regulators.
17. A system for calibrating analog circuits within an integrated
circuit, the system comprising: a core of the integrated circuit; a
microcontroller that is embedded in the integrated circuit, the
microcontroller including a processing unit and memory; a plurality
of sub-modules that includes the analog circuits therein; a
communication system arranged to communicatively interconnect the
microcontroller with the plurality of sub-modules for calibration
of the analog circuits therein; and a tangible non-transitory
storage medium for storing boot code for the microcontroller.
18. The system of claim 17, wherein the boot code comprises:
computer-readable program instructions for sending a reset control
signal to a sub-module of the plurality of sub-modules to reset an
analog circuit in the sub-module; computer-readable program
instructions for monitoring the communication system for a response
signal from the sub-module; computer-readable program instructions
for determining a calibration parameter for the analog circuit in
the sub-module based on the response signal; and computer-readable
program instructions for configuring the analog circuit in the
sub-module using the calibration parameter.
19. The system of claim 18, wherein the boot code further
comprises: computer-readable program instructions for repeating the
sending, monitoring, determining, and configuring for further
sub-modules of the plurality of sub-modules; and computer-readable
program instructions for communicating a signal from the
microcontroller to the core of the integrated circuit, the signal
indicating that calibration of the analog circuits in the plurality
of sub-modules is complete.
20. The system of claim 18, wherein the boot code further
comprises: computer-readable program instructions for sending a
reset control signal to the plurality of sub-modules such that
calibration-related processes for the plurality of sub-modules
proceed in parallel; computer-readable program instructions for
waiting to receive response signals from the plurality of
sub-modules, wherein a response signal for an individual sub-module
is received after an analog calibration-related process for the
individual sub-module is complete; computer-readable program
instructions for configuring the individual sub-module after the
response signal from the individual sub-module is received;
computer-readable program instructions for determining if all of
the plurality of sub-modules have been configured; and
computer-readable program instructions for waiting to receive
further response signals if not all of the plurality of sub-modules
have been configured.
Description
BACKGROUND
[0001] 1. Technical Field
[0002] The present invention relates generally to integrated
circuits, and more particularly to the calibration of analog
circuitry on integrated circuits.
[0003] 2. Description of the Background Art
[0004] As semiconductor process densities shrink, there is an
increasing number of different transistor level chip-to-chip and
on-die variations. Analog circuits, such as, differential receive
input buffers, for example, are very susceptible to such process
variations.
[0005] To compensate for such process variations, integrated
circuits may be manufactured with features to tune settings of
analog circuits so as to be able to compensate for these
variations. The tuning may be accomplished using calibration
procedures that may be implemented as dedicated circuitry that is
either hard-wired in the integrated circuit or configured into a
programmable core of the integrated circuit.
SUMMARY
[0006] The present disclosure provides apparatus and methods for
the calibration of analog circuitry on an integrated circuit.
[0007] One embodiment relates to a method of calibrating analog
circuitry within an integrated circuit. A microcontroller that is
embedded in the integrated circuit is booted up. A reset control
signal is sent to reset an analog circuit in the integrated
circuit, and a response signal for the analog circuit is monitored
by the microcontroller. Based on the response signal, a calibration
parameter for the analog circuit is determined, and the analog
circuit is configured using the calibration parameter.
[0008] Another embodiment relates to an integrated circuit
including a core, a microcontroller that is embedded in the
integrated circuit, a plurality of sub-modules that include analog
circuitry, and a communication system arranged to communicatively
interconnect the microcontroller with the plurality of sub-modules
for calibration of the analog circuitry.
[0009] Another embodiment relates to a system for calibrating
analog circuitry within an integrated circuit. The system includes
a core of the integrated circuit, a microcontroller that is
embedded in the integrated circuit, a plurality of sub-modules that
include the analog circuitry, and a communication system arranged
to communicatively interconnect the microcontroller with the
plurality of sub-modules for calibration of the analog circuitry.
The system further includes a tangible non-transitory storage
medium for storing boot code for the microcontroller.
[0010] Another embodiment relates to a programmable logic device.
The programmable logic device includes a programmable logic array,
a plurality of transceiver circuits, a microcontroller including a
processing unit and memory, and a communication system. The
communication system is arranged to communicatively interconnect
the microcontroller with the plurality of transceiver circuits for
calibration of analog circuits therein.
[0011] Other embodiments, aspects, and features are also
disclosed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 shows an exemplary integrated circuit that includes
an embedded calibration microcontroller and a common bus in
accordance with an embodiment of the invention.
[0013] FIG. 2 depicts an exemplary embedded calibration
microcontroller in accordance with an embodiment of the
invention.
[0014] FIG. 3 depicts an exemplary interface to a circuit module
having analog circuitry to be calibrated in accordance with an
embodiment of the invention.
[0015] FIG. 4A is a flow chart of a first exemplary serial method
of initially calibrating a plurality of analog circuits on an
integrated circuit in accordance with an embodiment of the
invention.
[0016] FIG. 4B is a flow chart of a second exemplary serial method
of initially calibrating a plurality of analog circuits on an
integrated circuit in accordance with an embodiment of the
invention.
[0017] FIG. 5A is a flow chart of a first exemplary parallel method
of initially calibrating a plurality of analog circuits on an
integrated circuit in accordance with an embodiment of the
invention.
[0018] FIG. 5B is a flow chart of a second exemplary parallel
method of initially calibrating a plurality of analog circuits on
an integrated circuit in accordance with an embodiment of the
invention.
[0019] FIG. 6 depicts exemplary analog circuits to be calibrated on
an integrated circuit in accordance with an embodiment of the
invention.
[0020] FIG. 7 is a simplified partial block diagram of an exemplary
field programmable gate array that may be configured to implement
an embodiment of the present invention.
[0021] FIG. 8 shows a block diagram of an exemplary digital system
that may employ techniques disclosed herein.
DETAILED DESCRIPTION
[0022] As described above, existing approaches to calibrating
analog circuits in an integrated circuit use calibration procedures
that are implemented as dedicated circuitry that is either
hard-wired in the integrated circuit or electronically-configured
into a programmable core of the integrated circuit. These existing
approaches have certain drawbacks and limitations.
[0023] Implementing the calibration procedures as hard-wired
circuitry in the integrated circuit has the advantage of being fast
in that it is brought up in a short amount of time. However, the
hard-wired circuitry suffers from the drawback of being inflexible
and requiring knowledge of the calibration algorithms prior to the
tape-out. This is substantial drawback because it may take months
of measurements across a large number of units to understand the
silicon process variations and their effect on the analog circuits.
There is also a risk of the calibration algorithms needing to be
changed after tape-out.
[0024] Implementing the calibration procedures using programmable
logic has the advantage of being flexible in that the calibration
algorithms may be changed by modifying the
electronically-programmed configuration of the programmable logic.
However, this approach typically requires the programmable logic
core of the integrated circuit to be programmed and ready before
the analog circuitry is operational. This may impede requirements
for a transceiver link bring-up time if the analog circuitry being
calibrated is needed by the transceiver circuitry.
[0025] The present disclosure provides an innovative new
architecture for calibrating analog circuits in an integrated
circuit. An embedded calibration microcontroller is provided within
the integrated circuit, and a common bus may be used to
communicatively couple the microcontroller to circuit modules
having analog circuitry to be calibrated.
[0026] Compared to the approach of hard-wiring the calibration
procedure, the presently-disclosed approach is slightly slower
because the procedure is performed by program code executed by the
microcontroller. However, the presently-disclosed approach has a
substantially lower risk of being unable to properly calibrate the
analog circuits. This is because only the processor and certain
peripheral interfaces are hard-wired, while the program code
provides flexibility in changing or adjusting the calibration
procedure.
[0027] Compared to the approach of configuring programmable logic
with the calibration procedure, the presently-disclosed approach is
substantially faster on the initial calibration. This is because
the programmable core of the chip does not need to be configured
prior to running the calibration procedure.
[0028] FIG. 1 shows an exemplary integrated circuit 100 that
includes an embedded calibration microcontroller 110 and a common
bus 112 in accordance with an embodiment of the invention. As
depicted, the common bus 112 may be arranged to use multiple lines
to communicatively interconnect the embedded calibration
microcontroller (referred to herein as the microcontroller or the
"EC.mu.C") 110 with a plurality of circuit modules 102 via the
interface (I/F) circuits 106. Each of the circuit modules may have
analog circuitry within one or more sub-modules 104. In addition,
the common bus 112 may be arranged to communicatively interconnect
to an interface to a core 120 of the integrated circuit 100. The IC
core 120 may include programmable circuitry and may be
electronically configured to include user code 122. In an exemplary
implementation, the common bus may implement an address based
read/write interface and may have separate address, data and
control lines.
[0029] FIG. 2 depicts an exemplary embedded calibration
microcontroller 110 in accordance with an embodiment of the
invention. As shown, the microcontroller 110 may include a
processing unit 202, memory for storing and accessing code (code
memory) 204, and timer circuitry 206. In an exemplary
implementation, the processing unit 202 may comprise an ARM.RTM.
(Advanced RISC Machine) core, and the code memory 204 may comprise
random access memory (RAM) for rapid access to the code. The timer
circuitry 206 may be arranged to provide timing signals for an
intra-chip communication system, such as, for example, the common
bus 112.
[0030] The microcontroller 110 may also include a debug module 208
which may utilize boundary scan technology for debugging the
processing unit 202. In an exemplary implementation, the debug
module 208 may implement a JTAG (Joint Test Action Group) boundary
scan test system. A test access port (TAP) 210 may be arranged to
interface to the debug module 208. The TAP 210 may be accessed via
a local input/output interface 212.
[0031] In an exemplary implementation, a controller block 220 on
the integrated circuit 100 may be arranged to receive or download
boot code 235 from a programmer object file 230. The boot code 235
may be stored by the controller block 220 into the code memory 204
of the microcontroller 110. The controller block 220 may be further
arranged to send a reset signal to the processing unit 202. Upon
being reset, the processing unit 202 may then execute the boot code
235 in the code memory 204.
[0032] FIG. 3 depicts an exemplary interface 106 to a circuit
module 102 having analog circuitry to be calibrated in accordance
with an embodiment of the invention. As shown, the interface 106
may include a memory-mapped port 302, a reset control circuit 304,
and a calibration configuration shift register (calibration CSR)
306.
[0033] The memory-mapped slave port 302 may be arranged to enable
addressing of a particular circuit module 102 amongst the N circuit
modules 102. The memory-mapped slave port 302 may be further
arranged to provide for addressing of a particular sub-module 104
within a circuit module 102. In an exemplary implementation, each
of the sub-modules 104 may be a physical media attachment (PMA)
module for a serial data channel, and each circuit module 102 may
include a triplet of three such PMA modules.
[0034] The reset control circuit 304 may be arranged to receive
reset control signals from the microcontroller 110 by way of the
common bus 112. The reset control circuit 304 may be further
arranged to send reset control signals to a selector circuit 308.
The selector circuit 308 may also receive reset control signals
from the IC core 120. The selector circuit 308 may be controlled by
an enable signal from the reset control circuit 304. For example,
if the enable signal is high, then the selector circuit 308 may
output the reset control signals from the reset control circuit
308, and if the enable signal is low, then the selector circuit may
output the reset control signals from the IC core 120.
[0035] The calibration CSR 306 may be arranged to receive
calibration control signals from the microcontroller 110 via the
common bus 112 and send calibration control signals to the analog
circuits to be calibrated within the circuit module 102. The
calibration CSR 306 may be further arranged to receive test data
signals from the sub-module 104 containing an analog circuit being
calibrated and send the test data signals to the microcontroller
110 via the common bus 112.
[0036] FIGS. 4A, 4B, 5A and 5B are flow charts of exemplary methods
(400, 450, 500, and 550, respectively) of initially calibrating a
plurality of analog circuits on an integrated circuit in accordance
with embodiments of the invention. The plurality of analog circuits
to be calibrated by these methods may be a subset or all of the
analog circuits on an integrated circuit. The plurality of analog
circuits to be calibrated may be pre-set during the design of the
integrated circuit or may be configurable by a user of the
integrated circuit. Furthermore, the plurality of analog circuits
may be of a same type of analog circuit or may include multiple
different types of analog circuits.
[0037] FIG. 4A is a flow chart of a first exemplary serial method
400 of initially calibrating a plurality of analog circuits on an
integrated circuit in accordance with an embodiment of the
invention. The method 400 calibrates the plurality of analog
circuits in a serial order. Blocks 403 through 430 of the method
400 may be performed by the embedded calibration microcontroller
(EC.mu.C) 110 executing instructions in the boot code 235.
[0038] Per block 401, after the IC 100 is powered on, the
controller block 220 may download the boot code 235 from the
programmer object file 230 to the code memory 204 of the EC.mu.C
110. Per block 402, the controller block 220 may then send a reset
signal to the processing unit 202 so that the EC.mu.C 110 begins to
execute the boot code 235.
[0039] Per block 403, the EC.mu.C 110 may wake-up analog circuit 1
of a plurality of N analog circuits. This step may be performed by
the EC.mu.C 110 sending via the common bus 112 a reset control
signal to the address associated with the sub-module 104 which
includes analog circuit 1.
[0040] Per block 404, the EC.mu.C 110 may monitor a response signal
of analog circuit 1 as a control parameter is varied. This step may
be performed by the EC.mu.C 110 receiving test data signals (in
this case, the response signal) via the common bus 112. The test
data signals may originate from the sub-module 104 which includes
analog circuit 1. For example, if analog circuit 1 is a phase
detector, then the test data signals may be the output signals of
the phase detector as its offset is varied. The offset may be
varied under control of the calibration control signals. In one
implementation, the calibration control signals may be sent from
the EC.mu.C 110 via a calibration CSR 306 to the phase detector
being calibrated.
[0041] Per block 406, the EC.mu.C 110 may determine one or more
calibration parameters for the analog circuit 1. The determination
may be performed by processing or analyzing the test data signals
received while monitoring the output of analog circuit 1. For
example, if analog circuit 1 is a phase detector, then the output
signals of the phase detector as a function of the offset may be
processed by an analysis procedure executed by the EC.mu.C 110. The
analysis procedure may check for the unstable state region of the
phase detector to determine the amount of offset cancellation that
is needed.
[0042] Per block 408, the EC.mu.C 110 may then configure analog
circuit 1. The configuration of analog circuit 1 may be performed
using the one or more calibration parameters determined per block
406. For example, if analog circuit 1 is a phase detector, then the
phase detector may be configured with an offset cancellation that
was determined using the analysis procedure executed by the EC.mu.C
110. The offset cancellation may be applied to the phase detector
by sending appropriate control calibration signals.
[0043] At this point in the method 400, analog circuit 1 has been
calibrated, and the method 400 moves on to calibrate a next analog
circuit. Per block 413, the EC.mu.C 110 may wake-up another of the
analog circuits, e.g., analog circuit 2 of the plurality of N
analog circuits. This step may be performed by the EC.mu.C 110
sending via the common bus 112 a reset control signal to the
address associated with the sub-module 104 which includes analog
circuit 2.
[0044] Per block 414, the EC.mu.C 110 may monitor the output of
analog circuit 2 as a control parameter is varied. This step may be
performed by the EC.mu.C 110 receiving test data signals (in this
case, the response signal) via the common bus 112. The test data
signals may originate from the sub-module 104 which includes analog
circuit 2. For example, if analog circuit 2 is a phase detector,
then the test data signals may be the output signals of the phase
detector as its offset is varied. The offset may be varied under
control of the calibration control signals. In one implementation,
the calibration control signals may be sent from the EC.mu.C 110
via a calibration CSR 306 to the phase detector being
calibrated.
[0045] Per block 416, the EC.mu.C 110 may determine one or more
calibration parameters for the analog circuit 2. The determination
may be performed by processing or analyzing the test data signals
received while monitoring the output of analog circuit 2. For
example, if analog circuit 2 is a phase detector, then the output
signals of the phase detector as a function of the offset may be
processed by an analysis procedure executed by the EC.mu.C 110. The
analysis procedure may check for the unstable state region of the
phase detector to determine the amount of offset cancellation that
is needed.
[0046] Per block 418, the EC.mu.C 110 may then configure analog
circuit 2. The configuration of analog circuit 2 may be performed
using the one or more calibration parameters determined per block
416. For example, if analog circuit 2 is a phase detector, then the
phase detector may be configured with an offset cancellation that
was determined using the analysis procedure executed by the EC.mu.C
110. The offset cancellation may be applied to the phase detector
by sending appropriate control calibration signals.
[0047] At this point in the method 400, analog circuit 2 has been
calibrated, and the method 400 moves on to calibrate a next analog
circuit. As indicated in FIG. 4A, the steps corresponding to blocks
413 through 418 are then performed for each subsequent analog
circuit, as desired, for example in the series of analog circuits
until analog circuit N is reached. In other words, the steps
corresponding to blocks 413 through 418 are then performed for
analog circuits 3 through N-1. The flow chart resumes at block 423.
It is appreciated that the calibration of analog circuits may be
performed in any order and that even some analog circuits may not
be calibrated on purpose. As such, calibration of the analog
circuits in series is exemplary and not intended to limit the scope
of the present invention.
[0048] Per block 423, the EC.mu.C 110 may wake-up analog circuit N
which is the last of the plurality of N analog circuits. This step
may be performed by the EC.mu.C 110 sending via the common bus 112
a reset control signal to the address associated with the
sub-module 104 which includes analog circuit N.
[0049] Per block 424, the EC.mu.C 110 may monitor the output of
analog circuit N as a control parameter is varied. This step may be
performed by the EC.mu.C 110 receiving test data signals (in this
case, the response signal) via the common bus 112. The test data
signals may originate from the sub-module 104 which includes analog
circuit N. For example, if analog circuit N is a phase detector,
then the test data signals may be the output signals of the phase
detector as its offset is varied. The offset may be varied under
control of the calibration control signals. In one implementation,
the calibration control signals may be sent from the EC.mu.C 110
via a calibration CSR 306 to the phase detector being
calibrated.
[0050] Per block 426, the EC.mu.C 110 may determine one or more
calibration parameters for the analog circuit N. The determination
may be performed by processing or analyzing the test data signals
received while monitoring the output of analog circuit N. For
example, if analog circuit N is a phase detector, then the phase
detector may be configured with an offset cancellation that was
determined using the analysis procedure executed by the EC.mu.C
110. The offset cancellation may be applied to the phase detector
by sending appropriate control calibration signals.
[0051] Per block 428, the EC.mu.C 110 may then configure analog
circuit N. The configuration of analog circuit N may be performed
using the one or more calibration parameters determined per block
426. For example, if analog circuit N is a phase detector, then the
phase detector may be configured with an offset cancellation that
was determined using the analysis procedure executed by the EC.mu.C
110. The offset cancellation may be applied to the phase detector
by sending appropriate control calibration signals.
[0052] At this point in the method 400, analog circuits 1 through N
have been calibrated, and the method 400 moves on to block 430. Per
block 430, the EC.mu.C 110 may send or communicate a signal to the
IC core 120 indicating that calibration of analog circuits 1
through N has been completed.
[0053] Alternatively, instead of sending the indication per block
430 after calibration of all the analog circuits 1 through N is
complete, an indication may be sent or communicated from the
EC.mu.C 110 to the IC core 120 after each individual analog circuit
is calibrated. Such an alternate serial method 450 is depicted in
FIG. 4B.
[0054] In comparison to the serial method 400 of FIG. 4A, the
serial method 450 of FIG. 4B includes new blocks 409, 419, and 429.
Per block 409, the EC.mu.C 110 may send a signal to the IC core 120
that the calibration of analog circuit 1 is complete after the
calibration of analog circuit 1 is done per block 408. Per block
419, the EC.mu.C 110 may send a signal to the IC core 120 that the
calibration of analog circuit 2 is complete after the calibration
of analog circuit 2 is done per block 418. Corresponding signals
may also be sent from the EC.mu.C 110 to the IC core 120 after the
calibration of analog circuits 3 through N-1. Finally, per block
429, the EC.mu.C 110 may send a signal to the IC core 120 that the
calibration of analog circuit N is complete after the calibration
of analog circuit N is done per block 428. Blocks 403 through 429
of the method 450 may be performed by the EC.mu.C 110 executing
instructions in the boot code 235.
[0055] FIG. 5A is a flow chart of a first exemplary parallel method
500 of initially calibrating a plurality of analog circuits on an
integrated circuit in accordance with an embodiment of the
invention. The method 500 allows for the calibration processes for
the plurality of analog circuits to proceed in a parallel manner.
Blocks 503 through 514 of the method 500 may be performed by the
embedded calibration microcontroller (EC.mu.C) 110 executing
instructions in the boot code 235.
[0056] Per block 501, after the IC 100 is powered on, the
controller block 220 may download the boot code 235 from the
programmer object file 230 to the code memory 204 of the EC.mu.C
110. Per block 502, the controller block 220 may then send a reset
signal to the processing unit 202 so that the EC.mu.C 110 begins to
execute the boot code 235.
[0057] Per block 503, the EC.mu.C 110 may wake-up sub-modules 104
which include analog circuits 1 through N of a plurality of N
analog circuits. This step may be performed by the EC.mu.C 110
sending via the common bus 112 a reset control signal to all the
addresses associated with the sub-modules 104 which include analog
circuits 1 through N.
[0058] Per block 504, the EC.mu.C 110 waits to receive response
signals. While the EC.mu.C 110 is waiting, a calibration-related
process may be performed at the sub-modules 104 which include the
analog circuits being calibrated. For example, if the calibration
involves voltage controlled oscillator (VCO) tuning, then the
calibration-related process may be tuning each VCO to a desired
receiving or transmitting frequency.
[0059] Per block 506, a response signal from an individual
sub-module 104 including analog circuit j may be received by the
EC.mu.C 110. For example, the response signal may be transmitted
from the calibration CSR 306 of the interface 106 of the sub-module
104 for the analog circuit j to the EC.mu.C 110 via the common bus
112. The response signal may provide calibration information for an
individual analog circuit j. For example, if the calibration
involves VCO tuning, then the calibration information may indicate
the control voltage (Vctrl) at which a frequency lock was
accomplished during the calibration-related process at the
individual VCO j. In some implementations, such a frequency lock
may take on the order of ten milliseconds to accomplish.
[0060] Per block 508, the EC.mu.C 110 may then determine one or
more calibration parameters for the analog circuit j. The
determination may use the calibration information received per
block 506. For example, if the calibration involves VCO tuning,
then the EC.mu.C 110 may use the received Vctrl to determine a gear
setting for the individual VCO j.
[0061] Per block 510, the EC.mu.C 110 may then configure the analog
circuit j. The configuration of analog circuit j may be performed
at the sub-module 104 that includes the analog circuit j using the
one or more calibration parameters determined per block 508.
[0062] Per block 512, a determination may be made as to whether all
the analog circuits 1 through N to be configured have been
configured. If not all the N analog circuits to be configured have
been configured, then the method 500 may loop back to block 504 and
wait to receive further responses. If all the N analog circuits to
be configured have been configured, then the method 500 may move on
to block 514. Per block 514, the EC.mu.C 110 may send a signal to
the IC core 120 indicating that calibration of the sub-modules 104
including analog circuits 1 through N has been completed.
[0063] Alternatively, instead of sending the indication per block
514 after calibration of all the N analog circuits to be configured
is complete, an indication may be sent from the EC.mu.C 110 to the
IC core 120 after each individual analog circuit of the N analog
circuits is calibrated. Such an alternate parallel method 550 is
depicted in FIG. 5B.
[0064] Blocks 503 through 515 of the method 550 of FIG. 5B may be
performed by the EC.mu.C 110 executing instructions in the boot
code 235. In the method 550 of FIG. 5B, block 514 of FIG. 5A is
effectively replaced by block 511. Per block 511, the EC.mu.C 110
may send a signal to the IC core 120 that the calibration of analog
circuit j is complete after the calibration of analog circuit j is
done per block 508. In addition, since the IC core 120 is signaled
after the calibration of each analog circuit is finished, once it
is determined that all analog circuits 1-N have been configured per
block 512, then the method 550 may be considered complete per block
515.
[0065] FIG. 6 depicts exemplary analog circuits that may be
calibrated on an integrated circuit 600 in accordance with an
embodiment of the invention. As shown, the integrated circuit 600
may include, for example, one or more transceivers 610. Each
transceiver may include, in its receiver path, input buffer 612,
equalizer 614, and clock-and-data recovery (CDR) circuit 616. Each
transceiver may also include one or more phase-locked loop (PLL)
circuits 622 and an output buffer (transmitter driver) circuit 624.
One or more voltage regulators 630 may also be included within the
integrated circuit 600.
[0066] Each of the depicted components may include at least one
analog circuit that may be calibrated by an embedded calibration
microcontroller in accordance with an embodiment of the invention.
For example, the CDR circuit 616 may include a phase detector (PD)
617 (which is a comparator), and the phase-locked loop 622 may
include a voltage-controlled oscillator (VCO) 623. The offsets for
multiple phase detectors on an integrated circuit may be
calibrated, for example, using a serial method such as one of the
methods (400 and 450) described above in relation to FIGS. 4A and
4B. Multiple VCOs may be tuned, for example, using a parallel
method such as one of the methods (500 and 550) described above in
relation to FIGS. 5A and 5B.
[0067] In addition, the equalizer 614 may include one or more sense
amplifiers 615. The sense amplifiers 615 include analog circuitry
and may be calibrated for offset correction. Multiple sense
amplifiers 615 may be calibrated, for example, using a serial
method such as one of the methods (400 and 450) described above in
relation to FIGS. 4A and 4B.
[0068] The output buffer circuit 624 also includes analog circuitry
and may be calibrated so as to reduce skew and duty cycle
distortion from its output signal. Multiple output buffer circuits
624 may be calibrated, for example, using a parallel method such as
one of the methods (500 and 550) described above in relation to
FIGS. 5A and 5B.
[0069] The voltage regulator 630 also includes analog circuitry and
may be calibrated to adjust its output voltage level. Multiple
voltage regulators 630 may be calibrated, for example, using a
serial method such as one of the methods (400 and 450) described
above in relation to FIGS. 4A and 4B.
[0070] It is contemplated that other analog circuits on an
integrated circuit may be calibrated using the techniques disclosed
herein. In general, such analog circuits may process or compare
analog signals and may be used for various applications, including
analog-to-digital conversion, signal filtering, and other control
and signal processing applications.
[0071] FIG. 7 is a simplified partial block diagram of an exemplary
field programmable gate array (FPGA) 10 that may be configured to
implement an embodiment of the present invention. It is to be
understood that FPGA 10 is described herein for illustrative
purposes only and that the present invention can be implemented in
many different types of integrated circuits, including FPGAs,
programmable logic arrays (PLAs), other programmable logic devices
(PLDs) including complex programmable logic devices (CPLDs),
digital signal processors (DSPs), central processing units (CPUs),
and application-specific integrated circuits (ASICs).
[0072] The FPGA 10 includes within its "core" a two-dimensional
array of programmable logic array blocks (or LABs) 12 that are
interconnected by a network of column and row interconnect
conductors of varying length and speed. The LABs 12 include
multiple (e.g., ten) logic elements (or LEs). A LE is a
programmable logic block that provides for efficient implementation
of user defined logic functions. An FPGA has numerous logic
elements that can be configured to implement various combinatorial
and sequential functions. The logic elements have access to a
programmable interconnect structure. The programmable interconnect
structure can be programmed to interconnect the logic elements in
almost any desired configuration.
[0073] FPGA 10 may also include a distributed memory structure
including random access memory (RAM) blocks of varying sizes
provided throughout the array. The RAM blocks include, for example,
blocks 14, blocks 16, and block 18. These memory blocks can also
include shift registers and FIFO buffers.
[0074] FPGA 10 may further include digital signal processing (DSP)
blocks 20 that can implement, for example, multipliers with add or
subtract features. Input/output elements (IOEs) 22 located, in this
example, around the periphery of the chip support numerous
single-ended and differential input/output standards. Each IOE 22
is coupled to an external terminal (i.e., a pin) of FPGA 10.
[0075] Physical coding sublayer (PCS) 29 and physical medium
attachment (PMA) 30 modules may be arranged as shown, for example,
with each PCS module 29 being coupled to several LABs. Each PMA
module 30 may be communicatively coupled to a corresponding PCS
module 29 and may include analog (and digital) circuitry to
implement one or more transceiver channels.
[0076] In accordance with an embodiment of the invention, the FPGA
10 may further include an embedded microcontroller 32 and a common
bus 33. The common bus 33 is arranged to communicatively
interconnect the embedded microcontroller 32 and the PMA modules
30. As described above, the embedded microcontroller 32 may be
utilized to advantageously implement methods of calibrating the
analog transceiver circuitry within the PMA modules 30.
[0077] It should be understood that embodiments of the present
invention can be used in numerous types of integrated circuits such
as, for example, FPGAs, FPGAs, PLAs, other PLDs including CPLDs,
DSPs, CPUs and ASICs.
[0078] FIG. 8 shows a block diagram of an exemplary digital system
50 that may employ techniques disclosed herein. System 50 may be a
programmed digital computer system, digital signal processing
system, specialized digital switching network, or other processing
system. Moreover, such systems can be designed for a wide variety
of applications such as telecommunications systems, automotive
systems, control systems, consumer electronics, personal computers,
Internet communications and networking, and others. Further, system
50 may be provided on a single board, on multiple boards, or within
multiple enclosures.
[0079] System 50 includes a processing unit 52, a memory unit 54,
and an input/output (I/O) unit 56 interconnected together by one or
more buses. According to this exemplary embodiment, FPGA 58 is
embedded in processing unit 52. FPGA 58 can serve many different
purposes within the system 50. FPGA 58 can, for example, be a
logical building block of processing unit 52, supporting its
internal and external operations. FPGA 58 is programmed to
implement the logical functions necessary to carry on its
particular role in system operation. FPGA 58 can be specially
coupled to memory 54 through connection 60 and to I/O unit 56
through connection 62.
[0080] Processing unit 52 may direct data to an appropriate system
component for processing or storage, execute a program stored in
memory 54, receive and transmit data via I/O unit 56, or other
similar function. Processing unit 52 may be a central processing
unit (CPU), microprocessor, floating point coprocessor, graphics
coprocessor, hardware controller, microcontroller, field
programmable gate array programmed for use as a controller, network
controller, or any type of processor or controller. Furthermore, in
many embodiments, there is often no need for a CPU.
[0081] For example, instead of a CPU, one or more FPGAs 58 may
control the logical operations of the system. As another example,
FPGA 58 acts as a reconfigurable processor that may be reprogrammed
as needed to handle a particular computing task. Alternately, FPGA
58 may itself include an embedded microprocessor. Memory unit 54
may be a random access memory (RAM), read only memory (ROM), fixed
or flexible disk media, flash memory, tape, or any other storage
means, or any combination of these storage means.
[0082] In the above description, numerous specific details are
given to provide a thorough understanding of embodiments of the
invention. However, the above description of illustrated
embodiments of the invention is not intended to be exhaustive or to
limit the invention to the precise forms disclosed. One skilled in
the relevant art will recognize that the invention can be practiced
without one or more of the specific details, or with other methods,
components, etc.
[0083] In other instances, well-known structures or operations are
not shown or described in detail to avoid obscuring aspects of the
invention. While specific embodiments of, and examples for, the
invention are described herein for illustrative purposes, various
equivalent modifications are possible within the scope of the
invention, as those skilled in the relevant art will recognize.
These modifications may be made to the invention in light of the
above detailed description.
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